Image forming apparatus

Abstract

In a heater including a plurality of first temperature detection elements that are arranged at predetermined intervals in a longitudinal direction of a substrate and respectively output temperature signals individually, and a plurality of second temperature detection elements that are arranged at predetermined intervals in positions that differ from the positions of the first temperature detection elements in a lateral direction that is orthogonal to the longitudinal direction but correspond to the positions of at least some of the plurality of first temperature detection elements in the longitudinal direction, and that output a single temperature signal obtained by adding individual temperature signals together, the individual temperature signals included in the single temperature signal are acquired on the basis of the plurality of temperature signals output by the plurality of first temperature detection elements and the single temperature signal.

The invention claimed is: 
     
       1. An image forming apparatus comprising:
 a fixing portion that includes a heater having a substrate, a plurality of heating elements arranged on a first surface of the substrate along a longitudinal direction of the substrate, and a plurality of temperature detection elements arranged along the longitudinal direction of the substrate on a second surface of the substrate opposite to the first surface, and that heats an image formed on a recording material so as to fix the image on the recording material using heat from the heater; and 
 a power control portion that controls power to be supplied to the plurality of heating elements on the basis of temperature signals output by the temperature detection elements, 
 wherein 
 the plurality of temperature detection elements include:
 a plurality of first temperature detection elements that are arranged at predetermined intervals in a longitudinal direction of the substrate and respectively output temperature signals individually; and 
 a plurality of second temperature detection elements that are arranged at predetermined intervals in positions that differ from the positions of the first temperature detection elements in a lateral direction that is orthogonal to the longitudinal direction but correspond to the positions of at least some of the plurality of first temperature detection elements in the longitudinal direction, and that output a single temperature signal obtained by adding individual temperature signals together, 
 
 each of the first temperature detection elements is respectively provided at a position corresponding to each of the plurality of heating elements in the longitudinal direction of the substrate, 
 each of the second temperature detection elements is respectively provided at a position corresponding to each of the plurality of heating elements in the longitudinal direction of the substrate, and 
 the apparatus further comprises a temperature acquisition portion that acquires the individual temperature signals included in the single temperature signal on the basis of the plurality of temperature signals output by the plurality of first temperature detection elements and the single temperature signal. 
 
     
     
       2. A heater for use in an image fixing apparatus for fixing an image formed on a recording material to the recording material, comprising:
 an elongated substrate; 
 heating elements arranged in a longitudinal direction of the substrate on a first surface of the substrate, wherein the heating elements are independently controllable; 
 a first conductor provided on a second surface opposite to the first surface of the substrate, the first conductor being provided over an entire area where the heating elements are provided in the longitudinal direction of the substrate; and 
 a second conductor provided on the second surface of the substrate, the second conductor being provided over the entire area where the heating elements are provided in the longitudinal direction of the substrate, 
 wherein the first conductor is provided on one end side of the substrate away from a center of the substrate in a lateral direction of the substrate perpendicular to the longitudinal direction of the substrate, and 
 wherein the second conductor is provided on the other end side of the substrate away from the center of the substrate in the lateral direction of the substrate. 
 
     
     
       3. The heater according to  claim 2 , further comprising a protective layer covering the first and second conductors,
 wherein one end and the other end of the first conductor in the longitudinal direction of the substrate and one end and the other end of the second conductor in the longitudinal direction of the substrate are exposed without being covered by the protective layer. 
 
     
     
       4. The heater according to  claim 3 , wherein the material of the protective layer includes glass. 
     
     
       5. The heater according to  claim 2 , further comprising a first temperature detection element for detecting a temperature of the heater,
 wherein the first temperature detection element is provided on the second surface of the substrate, and 
 wherein the first temperature detection element is electrically connected to the first conductor. 
 
     
     
       6. The heater according to  claim 5 , further comprising a second temperature detection element for detecting a temperature of the heater,
 wherein the second temperature detection element is provided on the second surface of the substrate, and 
 wherein the second temperature detection element is electrically connected to the second conductor. 
 
     
     
       7. The heater according to  claim 2 , wherein the substrate is made of ceramic material. 
     
     
       8. A fixing apparatus for fixing an image formed on a recording material to the recording material, comprising:
 a rotatable tubular film contacting the recording material; and 
 a heater provided in an inside space of the film, 
 wherein the heater is a heater according to  claim 2 . 
 
     
     
       9. The fixing apparatus according to  claim 8 , further comprising a roller contacting an outer surface of the film,
 wherein a fixing nip portion is formed by the heater and roller through the film, and the recording material is nipped and conveyed at the fixing nip portion. 
 
     
     
       10. A heater for use in an image fixing apparatus for fixing an image formed on a recording material to the recording material, comprising:
 an elongated substrate; 
 a heating element provided on a first surface of the substrate along a longitudinal direction of the substrate, the heating element being configured to generate heat when supplied with electric power; 
 a first temperature detection element for detecting a temperature of the heater, wherein the first temperature detection element is provided on a second surface opposite to the first surface of the substrate, 
 a first conductor provided on the second surface of the substrate, the first conductor being provided over an entire area where the heating element is provided in the longitudinal direction of the substrate; and 
 a second conductor provided on the second surface of the substrate, the second conductor being provided over the entire area where the heating element is provided in the longitudinal direction of the substrate, 
 wherein the first conductor is provided on one end side of the substrate away from a center of the substrate in a lateral direction of the substrate perpendicular to the longitudinal direction of the substrate, 
 wherein the second conductor is provided on the other end side of the substrate away from the center of the substrate in the lateral direction of the substrate, and 
 wherein the first temperature detection element is electrically connected to the first conductor. 
 
     
     
       11. The heater according to  claim 10 , further comprising a protective layer covering the first and second conductors,
 wherein one end and the other end of the first conductor in the longitudinal direction of the substrate and one end and the other end of the second conductor in the longitudinal direction of the substrate are exposed without being covered by the protective layer. 
 
     
     
       12. The heater according to  claim 11 , wherein the material of the protective layer includes glass. 
     
     
       13. The heater according to  claim 10 , further comprising a second temperature detection element for detecting a temperature of the heater,
 wherein the second temperature detection element is provided on the second surface of the substrate, and 
 wherein the second temperature detection element is electrically connected to the second conductor. 
 
     
     
       14. The heater according to  claim 10 , wherein the substrate is made of ceramic material. 
     
     
       15. A fixing apparatus for fixing an image formed on a recording material to the recording material, comprising:
 a rotatable tubular film contacting the recording material; and 
 a heater provided in an inside space of the film, 
 wherein the heater is a heater according to  claim 10 . 
 
     
     
       16. The fixing apparatus according to  claim 15 , further comprising a roller contacting an outer surface of the film,
 wherein a fixing nip portion is formed by the heater and roller through the film, and the recording material is nipped and conveyed at the fixing nip portion.